Hi all,

Just wanted to fill you in on a small UAV altitude record that was just set (still unofficial at the moment) using an autopilot similar to the ones discussed here. Here's a story about it: http://news.stanford.edu/news/2009/september14/airplane-self-pilot-091809.html

The record attempt was made by a group of graduate students who took a course this spring in the Aero/Astro Department at Stanford University. I was the teaching assistant for the course. This year the goal for the course was to design a small UAV to beat the remote control altitude record (~11, 000 ft). There were four teams of 4-5 students that had 10 weeks to go from a blank sheet of paper to a successful vehicle. The autopilot and propulsion system were provided, but the teams had to write their own control software and design/build the vehicles. The only sensor allowed was GPS (+ an barometric pressure sensor for the record attempt).

At the end of the class in June we had a flyoff where the teams had to demonstrate their vehicles by repeatedly climbing between 50 ft and 400 ft (to stay within FAA regulations). All four team succeed in demonstrating greater than 10,000 ft of cumulative altitude gain. A few students continued working on the project over the summer, culminating in a world record altitude attempt a couple weeks ago at the NASA Dryden Flight Research Center.

The altitude record attempt was for an autonomously controlled electrically powered UAV weighing less than 5kg, FAI Category U.2a Group 2. The news article gives a good account of the record attempt flights. The record altitude was 2177 m (7142 ft), which ended up being limited by winds aloft, not battery energy. Only about 40% of the charge was used getting to the record altitude.

Here are some pictures of the airplanes and the autopilot/GPS boards.

I designed and prototyped the autopilot for the course early this year. It uses the dsPIC30F4011 microcontroller and the uBlox LEA-5H + sarantel helical GPS antenna (basically the same as is being sold now, but in a slightly larger footprint). The xBeePro or xBeeProXSC is used for commands/telemetry. RC controller commands are read by the custom ground station software using a transmitter-to-USB cable and sent over the xBee to the airplane. This software based failsafe was not ideal, but it was the lightest option. The autopilot has inputs available for other sensors (thermopile, IMU), they just weren't integrated for the class and there isn't any software written to handle them.

If anyone is interested I should be able to post a BOM, the board files and the autopilot/ground station software, but it likely won't be supported at all since we are working on a smaller/lighter design to replace this one.


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Comment by Craig Palmer on September 20, 2009 at 5:35pm
Comment by bGatti on September 20, 2009 at 6:11pm
This is very interesting - especially as a comparison to the Ardupilot.

The use of xbee instead of transmitter is a much cleaner solution no? here's the catch, its slightly more expensive, especially since you also need a ground station interpreter. But it's not a dead end like the transmit option. Ironically, Arduino really can't do this because it has a single comm port. It bears mention that Microchip has recently purchased a C language interpreter, so the burden on a $300 interpreter is gone. They also have very nice low-end program/debugging options - cheaper than Atmel, Faster/better than Slowduino.

On the other hand, if they can do GPS-only, then Ardupilot can, and that would be a cheaper platform, even than this platform, due to the Xbee requirement. (idea for office pool, the date next month that Jordi flies ardu without sensors).

So the question - how does one make a stable aircraft; dihedral of course will take care of roll, for pitch stability, the plane must be heavy in the front, and must pitch upwards with increased speed. Such a design will nose down and accelerate until the speed pulls the tail down and the plane reaches equilibrium.

Sadly, such a design will never be much use in high or erratic winds. As the article states the record attempts were foiled by high winds aloft. Although i guess this was a matter of losing the plane downwind.

Good project.

Comment by Gary Mortimer on September 21, 2009 at 1:07pm
Makes me think we should have a free flight contest, lightest possible GPS logger on a very well made airframe with maybe one AA cell as the power source?

It would be I think, although I stand to be corrected totally outside of regulation.

What would it do?

Well it would put some better airframe designs on the table and be really low cost entry for younger individuals.

One of the benefits of now being an adult is, as long as I can get it past (or sneak it past) the minister of finance I can buy anything I need.

I'm old but I can so remember the pain of not being able to afford just a servo or a length of balsa.

For some people even at the relatively low cost of Ardu it must seem a high mountain to climb.

A free flight league would promote well setup airframes that most could afford.

Crikey, that was a rant.
Comment by Dimitar Kolev on September 22, 2009 at 3:09am
Great work, Geoff! I would be interested to take a look on BOM, schematics, etc. as you offered. Here is my email: dkolev@hotmail.com
Comment by Fahad Naseer on November 11, 2009 at 6:19am
how the helical antenna is for uav?


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